Lead is a well-recognized environmental and occupational toxicant that is widely distributed throughout the United States. Current research has suggested a variety of biological effects especially at high doses. These studies were an effort to find a more sensitive model for long-term low level lead exposure with analysis of serum gonadotropins and testosterone as well as sequential sperm analysis in rabbits as the end points for effect. The first year's study suggested that the low doses selected were effective in altering reproductive function and that this model will provide data for extrapolation of low dose effects of lead in men. Additional low dose groups were studied in the second of this series of investigations with greater focus on correlating blood levels with physiologically significant effects. All assay work has been completed and statistical analysis of the results are underway. We anticipate a better understanding of the direct effects of low level lead exposure on semen characteristics since preliminary analysis of the results suggests that major alterations in serum hormone parameters do not occur at the lower doses selected. (National Institute of Occupational Health and Safety subcontract)[unreadable]